AT&T MERLIN LEGEND System Reference Manual page 555

Hardware
Auxiliary Power Units
Protection Accessories
IROB Protection
The MFM comes complete with a D6AP cord, the KS22911 power unit, and a
400B or 400B2 adapter. DSSs are shipped without power units. Therefore, when
DSSs require local power, the KS22911 or 329A power unit. D6AP cord, and
400B or 400B2 adapter must be ordered separately.
Note: Telephone operation without adjuncts is guaranteed for a wiring run up to
1000 cable feet from the control unit.
When a power demand of over 54 unit loads is placed on one power supply
module, an Auxiliary Power Unit 9024 is generally required and increases power
by 27 unit loads. An auxiliary power unit is required when the unit loads on a
carrier exceed 54.
To determine
the number of unit loads
carrier, see "Unit Loads" in Chapter 6 and Appendix H.
Note: Only one auxiliary power unit can be connected to the 391A power unit. If
additional 48-VDC power is needed, connect some telephones to KS-22911 or
329A telephone power units.
Certain accessories are used for grounding and protecting special telephone
connections from power surges, electromagnetic interference, and electrostatic
discharge.
Equipment connected to the analog multiline telephone station jacks (on the
008, 408, and 408 GS/LS/TTR modules) or to the MLX telephone jacks (on the
008 MLX module) that is located in a different building but within 1000 cable feet
of the control unit requires IROB (in-range out-of-building) protection units.
These units protect the equipment and the control unit from lightning strikes and
power surges. Two units are required for each piece of equipment - one for the
control unit end of the wire run, the other for the equipment end.
Note: No 012 basic telephone modules can be used in IROB applications.
Use the following IROB protectors:
TII Model 343 (PEC32918) for analog multiline telephones and equipment
AT&T Model 505A (PEC32919) for MLX telephones and equipment
WARNING:
The IROB protectors must be installed by an AT&T service technician or a
qualified installer.
for each power supply module on each
Accessories 5-49